These are, to put it mildly, difficult times to be a Liberal Democrat. What is more, as Nick Clegg regularly tells colleagues, those times are about to get a whole lot worse. Lashed to the mast of a coalition with the Conservatives whose existence has made many of the party's erstwhile voters despair, the Lib Dem high command nevertheless feel compelled to stand up for coalition decisions on a range of policies with which many of its voters and activists, and even some ministers, disagree. Increasingly, the party is also taking real electoral punishment at the ballot box, with support in most opinion polls down by a half from 2010, knocked into sixth place in the Barnsley Central byelection last week and now facing a further pummelling when voters go to the polls in local and devolved elections at the start of May.

Yet to cut and run from the coalition is scarcely a credible option either. Not only do the parliamentary numbers stand in the way of any other configuration at Westminster until after a new general election. The hard truth also remains that the Lib Dems made the only plausible choice they could in the circumstances last year. To abandon the coalition now, just 10 months into what is supposed to be a five-year deal, would therefore be doubly devastating. The Lib Dems are fated to see it through and hope for better times ahead, as economic conditions perhaps improve and as enough middle-ground voters conclude that the shock treatment over the deficit was necessary. They, and we, are stuck with it.

What they – and the country – are not stuck with, however, is the requirement that the Lib Dems stare silently at their feet whenever the coalition does something particularly egregious – like the BSkyB decision last week – that was not in the agreement they struck last year. The top-down reorganisation of the National Health Service, a momentous and hazardous decision which was not in either party's own 2010 manifesto, and which was not in the coalition agreement either, is a particularly major example. Lib Dems are supposed to be defenders of the NHS. They are supposed to be supporters of an evolutionary, not a revolutionary, approach to reform. Whether on grounds of cost, accountability, the role of the private sector or patient choice, the NHS shakeup is not a policy that Lib Dems, even those who back the coalition, should support. On the contrary, they should oppose it. If they do not, one may ask, what is the point of their party?

Or take the question of the Tory side's increasingly strident approach to court decisions, here and in Europe, under the European convention or the Human Rights Act. A liberal party should always stand up strongly – though not of course uncritically – for the convention, for the courts, for international codes and for the Human Rights Act. Liberals should also make the reasoned argument for prisoners' votes, or for the right to seek review of the inclusion of one's name on a criminal register – the issues which have triggered the right's current campaign. Of course the issues are difficult. But the Tories are up for a fight on them. If the Lib Dems, of all parties, will not fight back and make the case for rights, who can?

The Lib Dems took an immensely difficult decision last year. Whether it will make them or finish them – or a bit of both – remains to be seen. There are still four years to go. A yes vote in May's alternative vote referendum would change the terms of politics significantly, perhaps allowing the party a hearing they do not now get. So might a sustained economic recovery of which there is currently not much sign. At the moment, however, the Lib Dems are not making their voice heard on issues where their voice ought to be. If the party is true to its liberal roots, as well as alive to its own self-interest, it must be willing to stand up for the values that helped raise the party to a position of power in the first place. If not now, when?